How many protons, neutrons, and electrons are present in an atom of hafnium, Hf, with a mass number of

178 106 protons, 72 neutrons,
106 electrons 178 protons, 250 neutrons,
72 electrons 72 protons, 178 neutrons, 106 electrons
72 protons, 106 neutrons, 72 electrons

106

props to the person above me

Explanation:

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: